Rhodium adlayers on Pt(111) monocrystalline surfaces.: Electrochemical behavior and electrocatalysis

Rh adlayers on Pt(111) electrodes have been prepared in two different ways from Rh3+ dilute solutions. The first layer grows in a pseudomorphic way whereas the second and subsequent seem to obey a pseudo-layer-by-layer growth: the third layer begins to form before the second is completed. Several adsorptive properties have been scrutinized: the adsorption of hydrogen and anions by means of voltammetry and charge displacement experiments and the adsorption of CO and NO by infrared spectroscopy. In general, it has been observed that the first layer (even at the level of submonolayer) shows a behavior in stark contrast with that of the Rh(111) and Pt(111) electrodes, whereas the behavior of the second layer is already akin to that;of the massive Rh(111) electrode. Although the monolayer probably presents strained Rh-Rh distances, the particular behavior of this adelectrode seems to be related to electronic perturbations caused by the underlying substrate. (C) 1998 Elsevier Science Ltd. All rights reserved.